Process for polymerizing a monomeric material in the presence of an insoluble salt of a fatty acid



United States Patent No Drawing. Filed Dec. 26, 1961, Ser. No. 162,223 The portion of the term of the patent subsequent to Jan. 26, 1982, has been disclaimed or dedicated to the Public 16 Claims. (Cl. 26084.1)

This invention relates to emulsion type vinyl aromatic resins and more particularly pertains to spherical, uniform particle size vinyl aromatic resins and to a process for preparing same in an aqueous emulsion comprising the use of polyvalent insoluble soaps as the sole emulsifiers.

The chemical literature reveals that several methods have been suggested for the provision of particular vinyl aromatic resins that are composed of spherical uniform particles. One of these references refers to a method for the provision of spherical uniform particle size polystyrene and styrene-butadiene latex resins wherein a soluble soap is used as the emulsifier in amounts insufiicient to establish the critical micelle concentration. Another method refers to a multiple-step procedure known as the seed-ing process wherein styrene-butadiene latex resins are prepared having spherical, uniform particles. Both the emulsifier deficient and the seeding process require highly critical techniques.

The uses of uniform particle size vinyl aromatic resins are many and diverse. For example, spherical, uniform particle size polystyrene latex resins are useful as secondary calibration standards for investigations in electron microscopy, light microscopy, light scattering, sedimentation studies and aerosol studies. Latex paint formulation theories state that there are reasons for believing that a film-forming, uniform particle size vinyl aromatic latex resin is desirable to minimize the problems of stability and reproducibility of flow properties. U.S. Patent 2,553,916 states that it is advantageous in synthetic resin paste formulations to bring about a paintable or pourable condition with a minimum of liquid plasticizer. U.S. Patent 2,553,916 teaches that powders of synthetic resins that are composed of a mixture of two uniform particle size resins with the larger uniform particle size resin having a particle size at least six times the size of the smaller uniform particle size resin requires a minimum of plasticizer.

It will become apparent from the discussion of our invention that our uniform particle size vinyl aromatic resins have utility in the aforementioned areas.

The use of materials commonly referred to as polyvalent insoluble soaps, polyvalent heavy metal soaps and polyvalent metallic soaps as the sole emulsifiers for the emulsion polymerization of vinyl aromatics or mixtures of vinyl aromatics with other polymerizable monomers was not known at the time of the present invention. The prior art does not teach. or suggest that such soaps would have any utility, per se, in the polymerization reaction. There is no indication in the prior art that such materials would have any value as emulsifiers in any aqueous system particularly in view of their 3,249,594 Patented May 3, 1966 "ice known limited solubility in water. The polyvalent insoluble soaps embodied herein are not regarded as emulsifiers for water systems. This invention, which is discussed in more detail below, is indeed unexpected in view of the prior art.

It is an object of this invention to provide vinyl aromatic resins that have spherical, uniform size particles. Another object of this invention is to provide spherical, uniform particle size vinyl aromatic resins in a single step polymerization. Still another object is the provision of a method for preparing spherical, uniform particle size vinyl aromatic resins having a predetermined particle size.

That the accomplishment of the foregoing and other objects have been achieved will become evident from the following description and examples.

We have discovered a method for preparing spherical, uniform particle size polyvinyl aromatic resins comp-rising conducting the polymerization of a monomer mixture of from 50 to by weight of at least one vinyl aromatic monomer and from 0 to 50% by weight of at least one other polymerizable monomer in water with agitation in the presence of a polyvalent insoluble soap as .the sole emulsifier.

Thus, the vinyl aromatic resins included herein are homopolymersof a vinyl aromatic monomer, copolymers and interpolymers of at least 50% by weight of a vinyl aromatic monomer and up to 50% by weight of one or more various other vinyl monomers copolymen'zable with the vinyl aromatic monomer. For the purpose of this invention, the vinyl aromatic monomer which may be homopolymerized or polymerized with one or more other vinyl monomers are those aromatic compounds that have one vinyl group and also have from 8-18 carbon atoms. The aromatic ring structure can be substituted in not more than two positions with a member selected from the group consisting of halide atoms and alkyl groups with 1 to 4 carbon atoms.' Such monomers include o-chlorostyrene, 2-chloro-4-bromostyrene, p-methylstyrene, 2-methyl-4-ethyl styrene and 2-chloro-4-methyl styrene. Also, the polymerizable vinyl part of the vinyl aromatic monomer may be substituted in the alpha position with a member selected from the group consisting of halides and alkyl groups of from 1 to 4 carbon atoms. Such monomers include alpha-methyl styrene and alphabromo styrene and the like. Also included are such monomers as alpha-chloro-p-chloro styrene and 3,4-di- -chloro-alpha-methyl styrene and the like.

The preferred vinyl aromatic monomer is styrene or a substituted styrene with the substitution being made on the ring in not greater than two positions and on the alpha carbon of the polymerizable vinyl group with a member selected from the group consisting of halide atoms and alkyl groups of 1 to 4 carbon atoms.

Most preferred are the vinyl aromatic monomers having the structure wherein R and R are each members selected from the group consisting of hydrogen, chlorine and an alkyl group having from 1 to 2 carbon atoms.

Included in the group of various other vinyl monomers copolymerizable with the vinyl aromatic constituent are those monomers having unsaturated groups selected from the class consisting of groupings. Such vinyl monomers include vinyl halides such as vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene bromide, vinylidene fluoride, chlorotrifluoro ethylene, 1,2-dichloroethylene, and the like; the acrylate and methacrylate esters such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, the butyl acrylates, the hexyl acrylates, the heptyl acrylates, the octyl acrylates, the dodecyl acrylates,phenyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, the propyl methacrylates, the butyl methacrylates, the amyl methacrylates, the hexyl methacrylates, the heptyl methacrylates, the octyl methacrylates, the nonyl methacrylates, the decyl methacrylates, the dodecyl methacrylates, phenyl methacrylates, cyclohexyl methacrylates and the like; the dienes such as 1,3-butadi- 'ene, 1,3-butadiene having the 2 position substituted with a member selected from the group consisting of halo atoms and alkyl groups of from 1 to 4 carbon atoms, 1,3-butadiene substituted at the 2 and 3 positions with members selected from the group consisting of halo atoms as 1,4-divinyl benzene, 1,3-divinyl benzene and the like and others.

Most preferred are the homopolymers, copolymers and interpolymers of from 50 to 100% by weight of styrene and from to 50% by weight of at least one other monomer selected from the group consisting of I 1120:0-0 0on5 wherein R is a chlorine atom, R is a member selected from the group consisting of hydrogen and chlorine, R and R are members selected from the group consisting of hydrogen, chlorine and an alkyl group containing from 1 to 2 carbon atoms, R and R are members selected from the group consisting of hydrogen and an alkyl group containing from 1 to 2 carbon atoms, and R is a hydrocarbon group containing from 1 to 12 carbon atoms. Even more preferred are the monomers in which R is an alkyl group containing from 1 to 8 carbon atoms.

The polyvalent metallic soaps or polyvalent insoluble soaps useful as the sole emulsifiers in the present invention include polyvalent metal salts of saturated, unsaturated and substituted fatty acids. The polyvalent moieties of the soaps embodied herein include in general any metals of Groups II, III and IV of the Mendelefis periodic table (the metals of said groups have a valency Within the range of two to four) and more particularly include beryllium, barium, calcium, magnesium, strontium, cadmium, zinc, lead, tin, titanium and aluminum. The fatty acid moieties preferred in the insoluble soaps embodied herein are octanoic, stearic, oleic, linoleic, ricinoleic, palmitic, abietic and the like. Most preferred are the monobasic saturated fatty acids having from 8 to 22 carbon atoms. useful in the range of from 0.01 part to 5 parts by weight The emulsifiers embodied herein are most 4 (per 100 parts of monomer) and preferably from 0.1 to 2.0 parts.

Most preferred in this invention are the insoluble soaps having the formula (A-COO) M wherein A is an alkyl group having from 7 to 21 carbon atoms and M is a member selected from the group consisting of barium, calcium, magnesium, cadmium, zinc, lead, tin and aluminumand n is an integer equal to the valence of M.

. erization.

The vinyl polymer latices of fine particle dispersions produced by the process of this invention generally contain polymer existing as uniform, spherical particles having average diameters of from 0.1 to 10 microns and more preferably from about 0.1 to 3 microns in diameter.

The process of this invention is carried out conveniently in a small polymerizer with stirring or in glass quart soda pop bottles, preferably in the substantial absence of elemental oxygen and in the presence of a free-radical initiator at a temperature of about C. or below, the temperature being measured at standard pressure. Thus, with superatmospheric pressure the reaction may be carried out at temperatures greater than 100 C. The polymerization reaction can be carried out at atmospheric, sub-atmospheric or superatmospheric pressure. Preferably, the polymerization is carried out at a reaction temperature in therange of from about 30 C. to 100 C., the temperature being measured at standard pressure. In general, the polymerization temperature chosen does not influence the particle size of the product, but those skilled in the art know lower temperatures tend to produce higher molecular weight polymers and higher temperatures tend to produce lower molecular polymers. It is also known that lower molecular weight resins soften at somewhat lower temperatures than their higher molecular weight analogues.

The free-radical initiators useful in the present invention include chemicals which decompose to produce free radicals under the foregoing reaction conditions as well as various forms of actinic radiation such as ultraviolet light, X-rays and the various types of nuclear radiation. Preferred as free-radical initiators in the present invention are commonly used polymerization initiators including the peroxides, azo compounds and redox catalysts. Most preferred are the water-soluble initiators such as potassium persul-fate, ammonium persulfate, sodium persulfate, hydrogen peroxide, potassium perphosphate and the like as well as the well-known water-soluble redox initiators. The free-radical initiator is most useful in the range of from about 0.01 part to 3 parts per hundred parts of monomer and more preferably from 0.05 part to 0.3 part per hundred of monomer.

Conventional emulsion polymerization buffers may be employed in the present process although they are not necessary for the practice of this invention. Buifers such as ammonia, NaHCO NH HCO and other water-soluble salts generally give slightly more stable latices. The pH of the polymerization mixture does not appear to be critical and it can be varied from about 2 to 10. However, a pH of between 6 and 10 is preferred.

In the novel polymerization process embodied herein the best results are obtained and the most stable latices result when mild but thorough agitation is employed.

Stated differently, the most stable latices result from the process embodied herein when good mixing with low shear stirring is-employed during the course of the polym- The use of high shear stirring is actually a convenient method to coagulate the latex if it is desired to do so either during or after completion of the polymerization reaction. The use of conventional emulsifiers as additional stabilizers after the completion of the polymerization reaction is within the scope of the present invention.

It is essential that the polymerization be carried to completion in the presence of the polyvalent insoluble soaps as sole emulsifier, however.

The vinyl aromatic resins embodied herein may be isolated from their latices by the use of conventional 6 latex was poured from the reactor. The latex was foun to have a pH of 6.5. A small sample of the latex was diluted with distilled water and the particle size and shape was determined by depositing a small amount of the methods of coagulation with such agents as sodium chlo- 5 diluted latex on a copper grid, carefully drying and takride, calcium acetate, sodium carbonate, alcohols, hying an electron photomicrograph of the deposited pardrochloric acid, sulfuric acid and the like by procedures ticles using a Philips (Model E.M. 100B) electron microwell known in the art. The vinyl aromatic resin latices scope. The latex particles were found to be very uniembodied herein can also be heat coagulated, shear form spheres having diameters of about 8,500 A. (0.85 Y coagulated, freeze coagulated, spray dried or coagulated 10 micron).

through water evaporation in film forming vinyl aromatic The remainder of the latex was coagulated and from resins. The coagulated resin is conveniently isolated by the weight of the coagulated polymer a 93 percent confiltration, centrifugation or decantation and may be dried version was calculated. About 91% of the polymer in in conventional drying equipment. this polymerization was obtained in latex form.

The polyvalent insoluble soaps embodied herein may Also, an analog of styrene, vinyl toluene was polymbe used per se or they may be generated in situ in the erized by the aforementioned procedure. The recipe polymerization mixture. When the soaps are used per consisted of 100 parts vinyl toluene, 0.1 part potassium se, it is generally necessary to homogenize the monomer persulfate, and 1.0 part barium laurate. A polymerizaprior to starting the polymerization. However, when tion temperature of 75 C. was employed. The reaction the insoluble soap is generated in situ, the homogenization was carried to an 87% conversion in 21 hours. A large step is usually not necessary. The insoluble soap such uniform particle size resin was obtained, similar to that as barium laurate may be generated in situ, for instance, obtained in the aforementioned styrene polymerization. by adding to the aqueous polymerization mixture substantially stoichiometric quantities of barium hydroxide E l 11 and lauric acid. 25

The vinyl aromatic resins embodied herein are ThlS ser es of polymerizatlons is similar to Example I tinguished from other conventional emulsion type vinyl that an 1801111916 P was used F l emulslfiel', aromatic resins in that the latter are not spherical, unibut the Polymerizatlons Ware earned out 111 one quart form particle size resins. For example, polystyrene presoda POP bottles pared with a conventional soluble soap emulsifier will f bottle thls serfs, unfier a nltrogen EVE/eel), usually have broad particle size distribution with the averdeWmerah-Zed Water, finely'dlvldecl insoluble P P hlghly age particle size generally less than 3,000 A. purlfied Styrene q wp ammonlum hydroxlde and P In the following examples which will serve to i11uS tassium persulfate initiator were added. The bottles were trate the process of the invention, the amounts of ingre- P Placed {natal shlelds and then Pl 111 a dients are expressed in parts by weight unless otherwise tamlg Polymenzatlon bath- A11 Polymenzafions were indicated' carried out at 75 C.

Example I Table 1 lists the members of this series indicating the insoluble soap emulsifier, levels of the constituents in the The polymerization was carried out in a small reacrecipe, reaction time, pH of the latex and particle size of tor equipped with a single blade stirrer. Into the reactor 40 the latex.

TABLE 1 Percent 28-30% Temp., Reaction Emulslfler Conver- H O KzSrOa HNrOH, pH C. Time, Particle Size sion ml. Hrs

Aluminum myristate 0.5 94 300 0.1 0.2 8.6 75 25.5 10,000 A. uniform.

Aluminum stearate 0.5 94 300 0.1 0.2 8.2 75 25.5 7,800 A.uniform.

Calcium laurate 0.5 93 300 0.1 0.2 8.4 75 25.5 9,200 A.uniform.

Calcium myristate 0.5 97 300 0.1 0.2 8.6 75 25.5 8,500 A.uniform.

Calcium palmitate 0.5 97 300 0.1 0.2 8.5 75 25.5 7,800 A. uniform.

Calcium stearate 0.5 97 300 0.1 0.2 8.4 75 25.5 10,800 A. uniform.

Magnesiumlaurate 0.5 97 300 0.1 0.2 8.4 75 25.5 12,000 A. uniform.

Magnesium myristate 0.5 99 300 0.1 0.2 8.5 75 25.5 9,000 A. uniform.

Magnesium stearate. 0.5 97 300 0.1 0.2 8.3 75 25.5 8,000 A. uniform.

Lead stearate 0.5 90 300 0.1 0.2 9.3 75 25.0 8,100 fairly Tetrastearyl tltanate 0.5 98 300 0.1 0.2 9.4 75 25.0 8,5 0 0 A fh 1 i1if0rm.

was charged 300 parts of demineralized water, 0.5 part Example III of finely-divided barium laurate and 100 parts of highly l v purified styrene monomer. The reactor was sealed and T1115 Series Of polymefllfltlons Was P p accofdlng then was alternately purged with nitrogen and evacuated. to the procedure used in Example II. The polymeriza- Next the reactor was pressured to 14 pounds per square tions of Example II, which are listed in Table 1, used a inch with nitrogen. The reactor was neXt submerged in 7 single insoluble soap as the sole emulsifier at a level of a 60 C. Wat r bath- The Styrene 1110mm? p (35 0.05 part per 100 parts of styrene monomer. In this hOmOgflIliZfid y alternately Stirling the mlXmTe series of polymerizations the single insoluble soap emulsiat 665 revolutions P mmute 9 one mlPute and then fier was replaced with a mixture of two insoluble soaps. quiescence for Thls i f Procedure The total insoluble soap level was the same as was used was repeated ten tunes h reactor .Snmng Speed was in Example II, that is, 0.5 part per 100 parts of styrene next reduced to 196 revolutions per minute and 0.2 part monomer of potasslum pirsu-lfate was 'ml-ected Into reactor' Table 2 lists the members of this series showing the in- The polymerization was carried out at 60 C. and 196 I 1 h revolutions per minute for about 41 hours. At the end solflble mixtures p ce t convers1ons, evels t e v of this period the reactor was Temoved f h h recipe constituents, final latex pH, reaction time and temand then allowed to cool. The resulting polystyrene perature and particle size.

TABLE 2 Percent 28% Temp, Reaction Cmulslfier Oonver- H2O Kzszos HN4OH, pH C. Time, Particle Size sion m1. Hrs.

Calciumlaurate... 0.25 95 300 0.1 0.2 0.3 74 25 0,000 A. fairly Magnesium laurat 0. 25 uniform. gglrgi unl nlldaggaigen 90 300 0.1 0.2 9.4 75 25 8,800 A. uniform. lllgdgglililgilllm fa 556.1 I 07 300 0.1 0.2 9.2 75 25 10,000 A. uniform.

l 3111'8 gggr l llinuigiestregtrate g. 95 300 0.1 0.2 9.4 75 25 7,800 A. uniform.

Example IV 3. The method of claim 1 wherein the insoluble soap In this series of polymerizations various representag of ilummum and a fatty and having from}; to tive copolymers of styrene were prepared according to .2 a g f 1 1 h h 1 b1 the procedure used in Example II. Table 3 lists these 20 6 met c alm W 61-61? t e insou e Soap copolymers The parts styrene comonomer parts, is a salt of cadmium and a fatty acid having from 8 to comonorner, polyvalent insoluble soap emulsifier, parts gi a f 1 1 h th 1 bl polyvalent insoluble soap emulsifier, percent conversion, 0 #3 2. u 3 polymerization temperature, reaction time and particle F Ca mum an a a y acl avmg to size for each copolymerization are shown. In all of these i d f I 1 h h 1 bl copolymerizations 0.1-0.2 part per 100 parts of mono- 0 w .31? e F u 3 mers of potassium persulfate was used as the initiator. 18 1 ea an a a y 361 avmg mm to 0.2 ml. ammonium hydroxide 2s 3-0% NH per 100 car parts of monomers was used as a butter in all styrene- The method 61mm 1 Whemm msohible soap acrylonitrile and styrene-butadiene copolymerizations. 3 mafneslum and a fatty acid havmg from Also, a terpolymer was prepared by the aforementioned 0 car on a Procedure The following recipe was used, 8. The method of claim l where in the insoluble soap Styrene 60; acrYlonitrile, 25; 13butadiene, 15; Potas 1s a salt of tin and a fatty acid having from 8 to 22 carsium persulfate, 0.1; barium laurate, 1,0, and ammonium bon atoms- 9. The method of clann 1 wherein the insoluble soap hydroxide, 0.2 ml.

All quantities are expressed in parts per 100 parts of 18 a Salt of Z1116 and a fatty acld having from 3 10 22 monomers, unless otherwise indicated. A polymerizaarb n atOm tion temperature of 75 C. was employed. A large uni- 10. The method for preparing a uniform particle size form particle size resin was obtained. vinyl aromatic resin having a particle diameter within TABLE 3 Parts Percent Temp, Reaction Styrene Comonomer Parts Emulsifler Oonver- C. Time, Hrs. Particle Size 90 Vinylidene chloride--. 10 Lead stearate 0.3 96 75 24 9,000 A.uniform.

d 10 Bariumlaurate 0.5 98 75 24 10,000 A.uniform.

Lead stearate..- 0.3 98 75 24 7,200 A. uniform. 50 Bariumlauratm 0.5 98 75 24 6,500 A. uniform. 15 do 1.0 98 75 18 6,400 A.uniform. 30 .do 1.0 95 75 is 5,900 A. fairly uniform. 1.0 97 75 18 800 A uniform 1.0 90 75 20.5 4,400A uniform 1.0 04 75 20.5 4,000A uniform 1.0 50 75 24 3,000A uniform 1.0 65 75 24 2,800 A uniform We claim: the range of 0.1 to 10 microns comprising polymerizing 1. The method for preparing in aqueous emulsion a in the presence of a free-radical catalyst and in the subuniform particle size styrene resin having a particle size stantial absence of oxygen a monomeric mixture of from within the range of 0.1 to 10 microns in diameter which 50 to 100% by weight of at least one, monomer having comprises polymerizing a monomer mixture of from 50 to the structure 100% by Weight of styrene monomer and from 0 to 50% by weight of at least one other unsaturated monomer I R 'copolymerizable with styrene, in water, with agitation .in the substantial absence of oxygen and in the presence zC=C of .a free-radical catalyst and, as the sole emulsifying agent, from 0.01 to 5.0 parts per 100 parts by weight of the monomer of an insoluble soap which is the salt of a B1 fatty acid having from 8 to 22 carbon atoms and a polyvalent metal of Groups II to IV of The Mendelefis periodic table.

2. The method of claim 1 wherein the insoluble soap where R and R are each members of the class consistis a salt of barium and a fatty acid having from 8 to ing of hydrogen, chlorine and an alkyl group having from 22 carbon atoms. 1 to 2 carbon atoms, and from 0 to 50% by weight of at 9 least one monomer selected from the group consisting of R2 4 5 R R1 11,0:(3: HzC=C-(iICHr,HzC=l}-CN, and Hr0=i1000R wherein R is chlorine, R is a member selected from the group consisting of hydrogen and chlorine, R and R are members selected from the group consisting of hydrogen, chlorine and an alkyl group containing from 1 to 2 carbon atoms, R and R are members selected from the group consisting of hydrogen and an alkyl group having from 1 to 2 carbon atoms, and R is a hydrocarbon group containing from 1 to 12 carbon atoms in water in the presence of from 0.01 part to 3.0 parts per 100 parts of monomers of a free-radical catalyst and from .01 to 5.0 parts per 100 parts of the monomers and as the sole emulsifier at least one polyvalent insoluble soap having the structure (A-COO),,M wherein A represents an alkyl group having from 7 to 21 carbon atoms and M is a member selected from the group consisting of barium, calcium, magnesium, cadmium, zinc, lead, tin and aluminum and n is an integer equal to the valence of M, with agitation in substantial absence of oxygen at a temperature below about 100 C.

11. The method for preparing a uniform particle size polystyrene resin having a particle diameter within the range of 0.1 to microns comprising polymerizing styrene in water in the presence of from .01 to 3.0 parts by weight per 100 parts of styrene of a free-radical catalyst and as the sole emulsifier from 0.01 to 5.0 parts by weight per 100 parts of styrene of at least one insoluble soap having the structure (A-COO),,M wherein A represents an alkyl group having from 7 to 21 carbon atoms and M is a member selected from the group consisting of barium, calcium, magnesium, cadmium, zinc, lead, tin and aluminum and n is an integer equal to the valence of M, with agitation in the substantial absence of oxygen at a temperature below about 100 C.

12. The method for preparing a uniform particle size polystyrene resin having a particle diameter within the range of 0.1 to 10 microns comprising polymerizing styrene in water inthe presence of from .05 to 0.3 part by weight per 100 parts of styrene of a free-radical catalyst and as the sole emulsifier from 0.1 to 2.0 parts by weight per 100 parts of styrene of barium laurate with agitation in the substantial absence of oxygen at a temperature of from about 30 C. to 100 C.

13. The method for preparing a uniform particle size polystyrene resin having a particle diameter within the range of 0.1 to 10 microns comprising polymerizing a monomer mixture of 50% to 100% by weight of styrene and 0 to 50% by weight of 1,3-butadiene in water in the presence of from .05 to 0.3 part by weight per 100 parts of said mixture of a free-radical catalyst and as the sole emulsifier from 0.1 to 2.0 parts by weight per 100 parts of said mixture of cadmium stearate with agitation in the 10 substantial absence of oxygen at a temperature of from about 30 C. to C.

14. The method for preparing a uniform particle size polystyrene resin having a particle diameter within the range of 0.1 to 10 microns comprising polymerizing a monomer mixture of 50% to 100% by weight of styrene and 0 to 50% by weight of methyl methacrylate in water in the presence of from .05 to 0.3 part by weight per 100 parts of said mixture of a free-radical catalyst and as the sole emulsifier from 0.1 to 2.0 parts by weight per 100 parts of said monomer mixture of barium laurate with agitation in the substantial absence of oxygen at a temperature of from 30 C. to 100 C.

15. The method for preparing a uniform particle size polystyrene resin having a particle diameter within the range of 0.1 to 10 microns comprising polymerizing a monomer mixture of 50% to 100% by weight of styrene and 0 to 50% by weight of acrylonitrile in water in the presence of from .05 to 0.3 part by weight per 100 parts of said mixture of a free-radical catalyst and as the sole emulsifier from 0.1 to 2.0 parts by weight per 100 parts of said monomer mixture of barium laurate with agitation in the substantial absence of oxygen at a temperature of from 30 C. to 100 C.

16. The method for preparing a uniform particle size polystyrene resin having a particle diameter wit-bin the range of 0.1 to 10 microns comprising polymerizing a monomer mixture of 50% to 100% by weight of styrene and 0 to 50% by weight of vinylidene chloride in water in the presence of from .05 to 0.3 part by weight per 100 parts of said mixture of a free-radical catalyst and as the sole emulsifier from 0.1 to 2.0 parts by weight per 100 parts of said monomer mixture of lead stearate with agitation in the substantial absence of oxygen at a temperature of from 30 C. to 100 C.

References Cited by the Examiner UNITED STATES PATENTS 2,777,836 1/ 1957 Everard 26029.6 2,888,410 5/ 1959 Bucholtz 2602.5 2,888,422 5/ 1959 Johnson et al. 26023 2,933,467 4/1960 Borunsky 26023 2,934,529 4/ 1960 Van Dijk et a1 26093.5 3,167,533 1/ 1965 Donat 26092.8

OTHER REFERENCES Hohenstein and Mark: Jour. of Poly. Sci., vol. 1, 1946, Polymerization of Olefins and Diolefins in Suspension and Emulsion, pp. 127-144.

Metallic Soaps, Metasap Chemical C0,, Harrison, N.J., copyright 1940, revised 1948, p. 19.

JOSEPH L. SCHOFER, Primary Examiner.

WILLIAM H. SHORT, Examiner.

M. F. OELAK, J. A. SEIDLECK, Assistant Examiners.

UNITED STATES PATENT OFFICE 7 CERTIFICATE OF CORRECTION Patent No, 3, 249, 594 May 3, 1966 Frank J. Donat et alm It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 65, for "OLOS" read w 0C5 columns 7 and 8, TABLE 2, heading to column 1, for "Cmulsifier" read Emulsifier same table, in the heading to column 5, for "HN OH" read NH OH column 7, line 34, for "1,0," read 1.0, column 9, lines 2 to 4, for

I R read 1'1 i same lines 2 to 4 for R read R 1 l H C= COOR H C= OOR Signed and sealed this 22nd day of August l967n (SEAL) Attest:

ERNEST W. SWIDER EDWARD JO BRENNER Attesting Officer Commissioner of Patents 

13. THE METHOD FOR PREPARING A UNIFORM PARTICLE SIZE POLYSTYRENE RESIN HAVING A PARTICLE DIAMETER WITHIN THE RANGE OF 0.1 TO 10 MICRONS COMPRISING POLYMERIZING A MONOMER MIXTURE OF 50% TO 100% BY WEIGHT OF STYRENE AND 0 TO 50% BY WEIGHT OF 1,3-BUTADIENE IN WATER IN THE PRESENCE OF FROM .05 TO 0.3 PART BY WEIGHT PER 100 PARTS OF SAID MIXTURE OF A FREE-RADICAL CATALYST AND AS THE SOLE EMULSIFIER FROM 0.1 TO 2.0 PARTS BY WEIGHT PER 100 PARTS OF SAID MIXTURE OF CADMIUM STEARATE WITH AGITATION IN THE SUBSTANTIAL ABSENCE OF OXYGEN AT A TEMPERATURE OF FROM ABOUT 30*C. TO 100*C. 